This web site contains various data files taken with our 3" NaI detector. The files are in ascii format, and are a listing of the counts recorded channel by channel. Our data acquisition card is a PCAE card from Oxford Instruments, and has 1028 channels. The ascii files below contain a listing of 1028 numbers starting with the counts recorded in channel number 0 and ending with the counts recorded in channel number 1027.

The files can be downloaded in ascii format and read into a spreadsheet for plotting and analysis.

A student written program is also available which can plot the data and perform Gaussian curve fitting for the photopeaks. The pascal version of the program is fitalle.pas . This program was written by students Byron Curry ('90) and Tsuyoshi Kawahito ('90). It performs Gaussian curve fitting for single and double peaks. It is designed to be used on the data listed below, and is written in pascal. For an executable version in DOS, left-click on the file fitalle.exe . You will also need the graphics driver egavga.bgi from Borland. This can be downloaded by left-clicking on egavga.exe . After this is saved on the hard disk, you must rename it to egavga.bgi. Both fitalle.exe and egavga.bgi along with any data files must be in the same directory for fitalle.exe to work.

Calibrated Gamma sources

The following spectra from sealed calibration sources were all taken using the same photomultiplier voltage of 650 volts, and the same amplifier settings: course gain = 80, fine gain = 0.9. All source have the same geometry with respect to the detector. They were placed at the center of one end of the 3 inch NaI detector. The activity is accurate to 4 percent.

The Na22 data file na22.dat was taken using a Na22 source which was 1.16 microcuries on December 11, 1984. Data was recorded for 300 seconds on June 3, 1998.

The Mn54 data file mn54.dat was taken using a Mn54 source which was 1.07 microcuries on April 5, 1991. Data was recorded for 300 seconds on June 3, 1998.

The Co60 data file co60.dat was taken using a co60 source which was 0.84 microcuries on March 13, 1985. Data was recorded for 300 seconds on June 3, 1998.

The Cs137 data file cs137.dat was taken using a Cs137 source which was 1.12 microcuries on April 30, 1985. Data was recorded for 120 seconds on June 3, 1998.

The Co57 data file co57.dat was taken using a co57 source which was 1.19 microcuries on March 26, 1991. Data was recorded for 300 seconds on June 2, 1998.

Some exercises one can do with the above calibration standards:

1. Identify the various parts of the spectrum: photopeaks, Compton regions, Compton edges, backscattering peaks, x-ray photopeaks.
2. Calibrate the energy in terms of the channel number. When this is done, try to identify the unknown isotope. This spectra is produced by one isotope. E-mail me your result, and I will let you know if you are correct.
3. Determine the efficiency of the detector as a function of energy (for the fixed geometry).

Soil and Sand Samples

This section contains gamma spectrum data for soil and other samples. Along with the soil samples are a background spectra, spectra due to Thorium(232), Uranium ore, and a pure KCl sample. The background, Th232, U238, and KCl spectra can be used as calibration standards to determine which isotopes (and their amounts) are in the various soil samples. This data allows students to investigate natural background radiation.

The file background data contains spectra data for a 1000 minute collection time. The detector was shielded with 5 cm of lead, no sample was present. The peak at channel number 820 is due to K40, from the detector, lead shielding and surroundings.

The file pure KCl crystals is the spectra for a 10 minute collection time for 3117 grams of pure potassium cloride crystals. The detector geometry for the KCl crystals is the same as all the soil samples listed below. This data can help calibrate how much potassium is in the soil samples.

The file uranium is the spectra from a uranium ore. The gamma spectra is due to the decay series of U238. This data can help determine if there is any uranium in the samples.

The file thorium is the spectra from a thorium sample. The gamma spectra is due to the decay series of Th232. This data can help determine if there is any thorium in the samples.

All the data below have the same detector geometry as the KCl standard and background listed above.

The file San Dimas soil is the spectra from a 1000 minute collection time of 3280 grams of soil from a backyard in the "old town" section of San Dimas. The sample was collected from my backyard.

The file Monrovia Foothills is the spectra from a 1000 minute collection time of 4735 grams of soil from the Monrovia Foothills. The sample was collected by Dr. Stefanie Saccoman.

The file Newport Beach Sand is the spectra from a 1000 minute collection time of 4778 grams of sand from Newport Beach (near the water). The sample was collected by Cal Poly Pomona student Vivienne Tran.

The file Big Bear dirt is the spectra from a 1000 minute collection time of 4468 grams of dirt from the Big Bear area. The sample was collected by Cal Poly Pomona student Cynthia Vazquez.

The file horse manure is the spectra from a 1000 minute collection time of 1049 grams of horse manure. The sample was collected by Cal Poly Pomona student Melissa Arredondo from her horse, who is fed here at Cal Poly Pomona.

Food samples for measuring Potassium Content

The data taken below were with our 3in NaI detector. Data was recorded for a 24 hour period.

The file bananas is the spectra from a 24 hour collection time of 2975 grams of bananas.

The file potatoes is the spectra from a 24 hour collection time of 3249 grams of potatoes.

The file prune juice is the spectra from a 24 hour collection time of 3102 grams of prune juice.

The file background is the spectra from a 24 hour collection time without a food sample.

Data to Determine Attenuation Coefficients

This section contains gamma spectrum data with different absorbers between the source and detector. The source used was Cs137, which gives off a gamma with energy 662 KeV and an x-ray with energy of 32 KeV. In the first set of data, we use lead absorbers of various thickness to attenuate the 662 KeV gamma particles. In the second set of data, we use aluminum absorbers of various thickness to attenuate the x-ray of 32 KeV. This data allows students to investigate Lambert's law and determine values for the attenuation coefficients of the 662 KeV gamma and the 32 KeV x-ray. All data were taken with the same source-detector geometry.

The file no absorber contains spectra data for the Cs137 source with no absorber. Collection time was two minutes. The 662 KeV photopeak is at around channel 390.

The file absorber C contains spectra data for the Cs137 source with a lead absorber of thickness 2.651 g/cm2. Collection time was two minutes. The 662 KeV photopeak is at around channel 390.

The file absorber D contains spectra data for the Cs137 source with a lead absorber of thickness 4.451 g/cm2. Collection time was two minutes. The 662 KeV photopeak is at around channel 390.

The file absorber E contains spectra data for the Cs137 source with a lead absorber of thickness 7.194 g/cm2. Collection time was two minutes.

The file absorber C and E contains spectra data for the Cs137 source with a lead absorber of thickness 9.845 g/cm2. Collection time was two minutes. The 662 KeV photopeak is at around channel 390.

The file no absorber contains spectra data for the x-ray of the Cs137 source with no absorber. Note: the amplification has been doubled from the previous 662 KeV data, so the x-ray peak can be more clearly measured. The x-ray photopeak is at around channel 90.

The file absorber 7 contains spectra data for the x-ray of the Cs137 source with an aluminum absorber thickness of 0.082 g/cm2. Note: the amplification has been doubled from the previous 662 KeV data, so the x-ray peak can be more clearly measured. The x-ray photopeak is at around channel 90.

The file absorber 13 contains spectra data for the x-ray of the Cs137 source with an aluminum absorber thickness of 0.342 g/cm2. Note: the amplification has been doubled from the previous 662 KeV data, so the x-ray peak can be more clearly measured. The x-ray photopeak is at around channel 90.

The file absorber 17 contains spectra data for the x-ray of the Cs137 source with an aluminum absorber thickness of 0.620 g/cm2. Note: the amplification has been doubled from the previous 662 KeV data, so the x-ray peak can be more clearly measured. The x-ray photopeak is at around channel 90.

The file absorber 20 contains spectra data for the x-ray of the Cs137 source with an aluminum absorber thickness of 0.961 g/cm2. Note: the amplification has been doubled from the previous 662 KeV data, so the x-ray peak can be more clearly measured. The x-ray photopeak is at around channel 90.

The file absorber 22 contains spectra data for the x-ray of the Cs137 source with an aluminum absorber thickness of 1.225 g/cm2. Note: the amplification has been doubled from the previous 662 KeV data, so the x-ray peak can be more clearly measured. The x-ray photopeak is at around channel 90.

The file absorber 25 contains spectra data for the x-ray of the Cs137 source with an aluminum absorber thickness of 1.602 g/cm2. Note: the amplification has been doubled from the previous 662 KeV data, so the x-ray peak can be more clearly measured. The x-ray photopeak is at around channel 90.

Data will be added to this section. If you want your own samples to be put on this web page, e-mail me at pbsiegel@cpp.edu.